The present invention relates to a new and improved method of operating an installation for processing waste paper.
Generally speaking, the waste paper processing installation operated according to the method of the invention contains a stock slusher or pulper and a device containing a housing which is arranged following the pulper with respect to the flow direction of the stock suspension. Within the housing there is arranged a closed defibering compartment or chamber, a rotor driven by a motor as well as a sieve or filter, at which merges a good stock chamber or compartment from which leads to the outside a good stock line or conduit. Additionally, there is provided at least one reject line leading from the defibering chamber towards the outside and serving for the elimination or separation of contaminants.
Waste paper processing installations of this type are known, for instance, from German Pat. No. 2,721,882, granted Jan. 18, 1979 and German Pat. No. 2,757,580, granted Mar. 15, 1979. The apparatus which is connected following the stock pulper, which is usually referred to in the art as a secondary pulper or fiberizer, is known for instance from U.S. Pat. No. 3,942,728, granted Mar. 9, 1976 and the corresponding German Pat. No. 2,345,735, granted Nov. 25, 1976.
Heretofore with the prior art installations the quantity of suspension which was separated out as a function of time was maintained constant, so that there was provided either a uniform flow through the reject line, or uniform periodic opening of a valve arranged in the reject line. The separation of the suspension charged with contaminants was accomplished independent of the content of contaminants, such as, for instance, foil pieces, pieces of solid wet paper which were not completely defiberized, or also heavy contaminants or particles and so forth.
Since these contaminants are present irregularly in processed waste paper, it was necessary to select the intensity of the separation operation, i.e. the quantity of suspension removed per unit of time, to be so great that there need not be feared any clogging of the apparatus, even in the presence of a maximum amount of contaminants which could be expected. This of course resulted in appreciable losses in energy and also good stock, since in the normal case it was necessary to remove too great a quantity of good stock along with the contaminants, of which only a part could be reclaimed.